Selective attention is a core cognitive ability that enables the processing of relevant stimuli while minimizing interference from irrelevant and/or distracting events. An overall goal of the research proposed here is to elucidate the neural mechanisms of attentional processes in order to test specific models of voluntary attention. In conjunction with psychophysical measures, event-related potentials (ERPs) will provide high temporal resolution measures of neural activity supporting attentional control and stimulus selection. Functional magnetic resonance imaging (fMRI) will be employed to identify the neuroanatomical systems and networks involved in attentional control and selection. This proposal has four specific aims: (1) Determine how changes in background neural activity in visual cortex during preparatory attention influence selective sensory processing and performance; (2) Determine the role of preparatory attention in establishing the locus of attentional selection during ascending sensory processing; (3) Determine the mechanisms of target facilitation and distracter inhibition processes in attentional selection; and (4) Determine how conflict monitoring / error detection systems interact with preparatory attention and selection mechanisms. Throughout the proposed research, the combined use of ERPs and fMRI will provide complementary measures of the time course and functional anatomy of attentional mechanisms. Because selective attention is a core cognitive process, elucidating attentional mechanisms in humans remains a high priority in efforts to understand, diagnose and treat psychiatric conditions that involve deficits in attention, including attention deficit hyperactivity disorder (ADHD), autism, obsessive compulsive disorder (OCD) and schizophrenia. [unreadable] [unreadable] [unreadable]